The present invention is directed to hole saws that have a waste plug or slug removal apparatus.
Hole saws are useful for cutting circular holes in a variety of materials, including, but not limited to wood, metal, plastics and dry wall. Hole saws are typically in the form of a hollow cylinder or tube having a circular edge with cutting teeth at one end and structure for attachment to a power drill or other type of drilling machine at the other end thereof. Typically, hole saws are sized and shaped to cooperate with the bit of a drill such that the cutting edge and possibly a portion of the flute of the bit extend in a direction forward of the circular cutting teeth of the saw to provide a center guide or pilot for placement of the hole in a desired location on a piece of material. In the art, the term “drill” may be used to describe a drilling machine or a drill bit for use in a drilling machine. Therefore, in this application, for the sake of clarity, the term “drill bit” or “bit” is used throughout to refer to a bit for use in a drilling machine, and “drill” always refers to a drilling machine, such as a power drill.
As a pilot drill bit and cooperating hole saw rotate, a desired hole is cut in a piece of material, leaving an unwanted or waste plug of the material located within the cylindrical wall of the tubular hole saw. Various structure and mechanisms have been devised to remove or allow for easy removal of the plug formed within the hole saw. For example, some hole saws include radially inwardly and outwardly directed teeth to provide adequate space or clearance to allow for the plug to drop out of the hole saw after sawing of the hole. However, plugs often get stuck within the saw and knock-out devices have been devised that eject such plugs after a hole is completed. Some knock-out devices have included a plate or other structure cooperating with a spring located within the tubular body of a hole saw. Such plates or other structures include a central aperture for completely clearing the pilot drill bit. As the hole saw is used, the knock-out plate or other structure is pushed against the spring by the plug of material being formed during the hole sawing process, moving the knock-out plate away from the cutting teeth and compressing the spring. When the hole is completed and the saw's rotation is stopped, the spring decompresses and pushes the knock-out plate against the waste plug, pressing the plug in a linear direction along the central axis of the hole saw and toward the cutting teeth and ultimately out the end of the saw. Particles and dust from the sawing of the hole however, may slow, hinder or even stop such linear movement of the waste plug out of the hole saw. One known prior art mechanism includes a knock-out plate retained within a hole saw by screws that extend radially outwardly through clean-out slots located on the cylindrical wall of the saw. The screws also attach to an external ring that may be grasped and forced along the curved clean-out slot path at the outer surface of the saw, thus pushing the knock-out plate and the waste plug toward the cutting teeth and out of the saw. A compression spring located within the hole saw aids in positioning and ejecting of the waste plug.